JP2705018B2 - Discharge lamp lighting device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a lighting device for a discharge lamp.

(Prior art)

Generally, in order to light a discharge lamp, a lighting device commonly called a ballast is used. In the past, this ballast had a major drawback of heavy weight, but recently, an ultra-small and lightweight ballast has been developed by an open / close control method using a semiconductor switching element.

In order to light the lamp by such a device, first, the starter causes dielectric breakdown between the electrodes of the discharge lamp. Thereby, conduction between the electrodes is momentarily conducted. The voltage at this time is usually called a dielectric breakdown voltage, and after charging the dischargeable voltage in the charge / discharge capacitor in the starter, the battery is discharged toward the discharge lamp. This breakdown voltage is, for example, 20
In the case of a V100W ultra-high pressure mercury lamp, it is about 1500V.

When the dielectric breakdown voltage causes conduction between the electrodes, the main lighting circuit having the semiconductor switching element supplies a current that meets the standard of the discharge lamp to perform stable lighting.

[Problems to be solved by the invention]

However, in the case of such a lighting device, in order to perform good lighting, the discharge state in the lamp when the dielectric breakdown is caused by the starter is reduced to a state where the current supply from the next main lighting circuit to some extent can be received. Must be migrated. (Such a state is usually called an arc discharge state.) However, in reality, it is not easy to bring this state by one operation of the starter. In such a case, the discharge lamp does not fall off or remains glow discharge without being switched to arc discharge, and substantially fails to light.

(Object of the present invention)

Therefore, an object of the present invention is to provide a lighting device capable of promptly shifting to a stable lighting state after a dielectric breakdown of a discharge lamp with a simple circuit configuration.

[Means for solving the problem]

In order to solve the above object, a lighting device of the present invention includes a discharge lamp, a main lighting circuit for lighting the discharge lamp by opening and closing control of a semiconductor switching element, and is connected in parallel with the discharge lamp, and before starting lighting. A starter having a charge / discharge capacitor that performs charging and discharges toward the discharge lamp after being charged to a voltage at which dielectric breakdown is possible,
A discharge lamp lighting device comprising a timer circuit for driving the starter for a predetermined time after the discharge lamp is insulated by the discharge of the charge / discharge capacitor, wherein the starter is configured such that the discharge lamp is insulated. After the breakdown, a means for supplying a continuous current to the discharge lamp, not a pulse current due to the charge / discharge capacitor, to shift from an unstable lighting state after insulation breakdown to a stable lighting state. It is characterized by the following.

[Action]

According to the lighting device having such a configuration, the starter continues to operate for the time set in the timer circuit even after the high voltage is supplied to the discharge lamp to cause the dielectric breakdown. At this time, since the current supplied from the starter has a reduced lamp voltage, substantially a continuous current is supplied instead of the pulp current by the charging / discharging capacitor. Then, the lighting state of the lamp can be shifted in a stable manner, and the current from the non-lighting circuit can be favorably received.

〔Example〕

Hereinafter, a specific description will be given using examples. FIG. 1 is a schematic view of a discharge lamp lighting device according to the present invention. In the figure, reference numeral 1 denotes a discharge lamp, for example, a super high pressure mercury lamp of 20V100W is applied. (The discharge lamp 1 will be simply referred to as a lamp hereinafter.) Reference numeral 2 denotes an AC power supply, for example, 100 V, 50 Hz. A main lighting circuit 3 is connected to the AC power supply 2, from which current is supplied to the lamp 1. A starter 4 supplies a high voltage (dielectric breakdown voltage) to the lamp 1 at the start of lighting to cause dielectric breakdown.

When the switch 61 is first turned on, the operation of the starter 4 is linked and the relay 47 is closed. As a result, the current from the AC power supply 48 passes through the resistor 46 and the diode 45,
Filled into 44. Then, when the charging voltage of the capacitor 44 reaches the breakdown voltage of the thyristor 43, the capacitor 44 discharges, and this discharging voltage is boosted by the transformer 42, and passes through the diode 41 and the resistor 52. (Referred to simply as a capacitor). And the charging voltage of the condenser 51 is changed to the lamp 1
The capacitor 51 discharges toward the lamp 1 when the voltage reaches the point at which the dielectric breakdown can occur. The breakdown voltage at this time is about 1000 to 1500 V in the case of the lamp of the above standard.

Due to this dielectric breakdown, the lamp 1 conducts momentarily and starts lighting. Here, the relay 47 of the starter 4 keeps closing for a predetermined time after the switch 61 is turned on by the operation of the timer circuit 6. Therefore, even after the breakdown of the lamp 1, the starter 4 repeats the above operation. Therefore transformer 42
A pulse current is generated again on the secondary side of. FIG. 3 is a circuit diagram showing the state of charging and discharging of the capacitor 51 after the lamp 1 has been broken down. The pulse current passing through the diode 41 is rectified and smoothed together with the capacitor 51 and flows through the lamp 1. This is because the impedance of the lamp 1 after dielectric breakdown becomes low. For this reason, the charging / discharging capacitor 51 that has supplied a high voltage before the dielectric breakdown substantially loses its function. The current I1 differs depending on the state of the dielectric breakdown of the lamp 1. For example, when the first dielectric breakdown is not performed well, the impedance of the lamp 1 is still high, so the current I1 is very small. And again capacitor 51
Provides a high voltage for dielectric breakdown. On the other hand, when the first dielectric breakdown causes conduction between the electrodes and the lamp 1 enters a glow discharge state, a current sufficient to shift to an arc discharge state is supplied. This is because the impedance of the lamp 1 itself after the dielectric breakdown is smaller than that before the dielectric breakdown. This current I1 depends on the state of the lamp 1 after dielectric breakdown,
It is set appropriately according to the ratio of the impedance of the series circuit 5 of the capacitor 51 and the resistor 52. It is desirable to connect the resistor 52 in order to make the lamp 1 satisfactorily shift to the stable lighting state, but it is not always necessary. Here, a choke coil or the like may be used as the resistor 52 as long as it has impedance. On the other hand, for the lamp 1, from this glow discharge to the state in which the supply current from the main lighting circuit can be well received by this current I1 (arc discharge)
Then, the lighting is stabilized by the supply current from the main lighting circuit 3. The time for supplying the current I1 can also be appropriately determined by the set time of the timer circuit 6 and the impedance of the resistor 52 and the capacitor 51.

FIG. 2 shows a lamp 1 according to the lighting device of the present invention.
5 shows a voltage change from the start of lighting to the transition to a stable lighting state. The vertical axis shows the voltage of the lamp 1, and the horizontal axis shows time. In FIG. 2, when the breakdown voltage Vs is applied to the lamp 1 from the starter 4 at the time a, the glow discharge state is established and the voltage drops rapidly. Then, from the starter 4, the pulse current I1
(Superimposed voltage Vo) is subsequently supplied to shift from an unstable glow discharge state to an arc discharge state. (Period b in the figure) Then, current is supplied from the main lighting circuit 3 at the voltage Vi, and the lamp 1 is stably lit.

(Period c in the figure) When the above-described lamp 1 is used, the superimposed voltage Vo is about 80 to 100 V, and the period b is about 100 to 300 μsec.

The main lighting circuit 3 will be described in detail.
Is converted into a DC output by a rectifying / smoothing circuit 31, and in a switching circuit 32, a semiconductor switching element provided therein is controlled to open and close. This open / close control detects the lighting voltage and lighting current of the lamp 1 and performs feedback control. (Not shown) Switching circuit
The output of 32 passes through a transformer 33 and a diode bridge 34,
Further, it is smoothed by the choke coil 35 and the condenser 36 and flows to the lamp 1 via the diode 37. The diode 37 is an element for preventing a reverse current from flowing from the starter 4 to the main lighting circuit.

〔The invention's effect〕

As described above, according to the discharge lamp lighting device of the present invention, with respect to the lighting, a breakdown voltage is first supplied from the starter, and a continuous current is subsequently supplied from the starter. Therefore, the discharge lamp can be surely shifted to a stable state, and its circuit can be simply constructed.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a discharge lamp lighting device according to the present invention.
FIG. 2 is a graph showing the change of the voltage of the discharge lamp with respect to time. FIG. 3 is a partial circuit diagram showing another embodiment of the present invention. In the figure, 1: Discharge lamp 3: Main lighting circuit 4: Starter 5: Charge / discharge circuit 6: Timer circuit 10: Lamp circuit 51: Capacitor 52: Impedance element

Claims (1)

(57) [Claims] 1. A discharge lamp, a main lighting circuit for lighting the discharge lamp by opening / closing control of a semiconductor switching element, connected in parallel with the discharge lamp, charging before starting the lighting, and reaching a voltage at which a dielectric breakdown is possible. A starter having a charge / discharge capacitor that discharges toward the discharge lamp after being charged; and a timer that drives the starter for a predetermined time after the discharge lamp has been broken down due to discharge of the charge / discharge capacitor. A discharge lamp lighting device comprising a circuit, wherein the starter causes the discharge lamp to supply a continuous current, not a pulse current due to the charge / discharge capacitor, after the dielectric breakdown of the discharge lamp. Discharge lamp comprising means for shifting from an unstable lighting state to a stable lighting state after insulation breakdown. Lighting device.